Attention

References 1. Kastner S, Ungerleider L, Annual Reviews Neuroscience, vol 23, pp. 315-341, 2000 2. Gitelman DR, Attention and its disorders, British Medical bulletin, vol 65, pp.21-34, 2003 3. Naghavi H, Nyberg L, Common fronto-parietal activity in attention, memory and consciousness, Consciousness and cognition, vol 14, pp. 390-425, 2005

Attention is not a unitary concept, but it represents a cohesive set of processes which serve to enhance sensory, motor, cognitive processing Subsystems in attention: (Posner, 1990) 1. Orienting to sensory events --> visual system 2. Detecting signals for focal (conscious) processing --> frontal semantic sys. 3. Maintaining an alert state --> arousal system Gitelman, 2003

Attention studies: Intentional attention: (Frontal systems) Selective attention: choosing a particular target among multiple input streams Divided attention: monitoring of several stimuli at the same time Vigilance: sustained attention 1. devoting attention to a particular stimulus over time 2. reactive attention: detection and response to any unpredictable event (superior coll., brain stem and thalamic mechanisms)

Gitelman, 2003

Arousal: sustained attn Executive process: shifting attn. (top-down) Sensory process: attending stımuli (bottom-up) Gitelman, 2003

Fronto-parietal activity: * Activity in the precentral, intraparietal and occipital gyri occur for both overt (explicit eye movement) and covert (no eye movement) attention shift tasks * The fronto-parietal activity persists in attention studies that involve other modalities than visual attention * The fronto-parietal activity is present in both endogeneous (voluntary) and exogeneous (stimulus-driven) types of attention. Right DLPFC selectively became activated for the endogeneous attention studies. Bilateral frontal and bilateral parietal activity observed for both endogeneous and exogeneous attention tatsks.

Can attention modulate stimulus-processing in sensory areas? * While viewing the same achromatic pattern on screen, motion processing areas in occipital cortex activate if the subject is informed to detect motion but color processing areas in visual cortex activate if the subject is told to detect changes of color * Seems like top-down processes generate a preparatory state for consequent bottom-up sensory processing

Effects of selective attention on neural processing: 1. Enhances neural response to attended stimuli 2. Filters unwanted information by counteracting the suppression effect of nearb distractors 3. Biases signals in favor of attended location (incerase in baseline activity even when stimulus is not present 4. Increases stımulus salience by increasing neuron's sensitivity to stimulus contrast

Example The limited sensory processing capabilities cause competition in the visual field for neuronal representation when multiple objects are presented (eg: 2 objects given, attend to color of one, orientation of the other) location bias stimulus salience Competition bias (Kastner, Ungerleider, 2000)

(location bias) (stimulus salience) (Kastner, Ungerleider, 2000)

A COMMON FRONTO-PARIETAL NETWORK IN A MULTITUDE OF PROCESSES

The global workspace concept: Naghavi, Nyberg, 2005

Naghavi, Nyberg, 2005

Naghavi, Nyberg, 2005